摘要
目的探讨Z轴管电流调制技术对多层螺旋CT颈部扫描的图像质量和辐射剂量的影响。方法将120例进行多层螺旋CT颈部扫描的受检者随机分为Z轴管电流调制组(试验组)和管电流固定组(对照组),每组各60名。试验组的目标噪声水平设置为7.5HU,管电流的动态范围为40～500mA,对照组的管电流设置为250mA,其他扫描参数两组完全相同。分别记录两组受检者的CT剂量容积(CTDIvol)和剂量长度乘积(DLP)、记录管电流调制组甲状腺峡部层面的管电流值,测量下颌角、甲状腺峡部、胸骨上切迹层面的图像噪声,图像质量分3级(优、良、差),由2名有经验的CT主管技师和一名主任医师进行双盲法评价。计数资料采用成组设计的X2检验,计量资料采用成组设计的t检验,P<0.05为差异有统计学意义。结果试验组CTDIvol,DLP和甲状腺峡部层面毫安值的平均值分别为21.4mGy,210.5mGy·cm和120.5mA;对照组的分别为13.8mGy,292.8mGy·cm和250mA,试验组较对照组分别增加90%,降低28%和降低47%,两组差异有统计学意义(P值均<0.05)。试验组下颌角和甲状腺峡部层面的图像噪声分别为7.36HU和7.05HU,稍高于对照组的5.64HU和4.85HU;试验组胸骨上切迹层面的图像噪声为7.23HU,明显低于对照组的13.24HU,下颈部图像质量优的数量大幅增加。结论 Z轴管电流调制技术根据受检者体型和受检部位密度厚度变化在每周旋转均对管电流进行动态调整,使辐射剂量的分布实现了个性化,保证了不同层面图像质量的恒定,在多层螺旋CT颈部扫描时可降低辐射剂量并提高图像质量,在临床CT扫描中有很大应用价值。
Objective To study the effect of Z-axis tube-current modulation technique to image quality （image noise level） and radiation dose of MSCT （16-slice CT） in neck scanning. Methods Consecutive 120 patients underwent neck CT were randomly divided into two groups： Z-axis tube-current modulation （ZTCM） group （test group） and constant tube-current （CTC） group （contrast group）. The desired noise level of ZTCM group was 7.5HU and the dynamic tube-current range was 40i 〈〈500mA, the tube-current of CTC group was set 250mA, while the other scan parameters remained totally same. CTD1vol and DLP of two groups, the tubecurrent of image at thyroid isthmus slice of ZTCM group were recorded respectively. The noise index level of image at angle of mandible, isthmus of thyroid, suprasternal notch were measured and compared. The qualities of hnages were classified in three levels （excellent, good, poor） with double blind method. Results CTDIvol, DLP and the tube-current of image at thyroid isthmus slice ZTCM group were 21.4 mGy, 210.5mGy .cm and 120.5mA, those of CTC were 13.8 mGyi 292.8 mGy. cm and 250mA, ZTCM group increased 55%, decreased 28% and decreased 52% respectively as compared with CTC group. The noise index of image at angle of mandible and isthmus of thyroid were 7.36 HU and 7.05 HU in ZTCM group, those were a little higher than CTC group of 5.64HU and 4.85 HU, the noise index of image at suprasternal notch was 7.23HU in ZTCM group, it was significantly lower than CTC group of 13.24HU, the cases of excellent images in ZTCM group was significantly higher than that of CTC group （P 〈 0.05）. Conclusion ZTCM technique dynamically modulates tube current every gantry rotation according to the patients＂ habitus, thickness and density of scan position, it realizes individua- tion and keep images qualities constant of different slice. It decreases the total radiation dose and improves image quality in neck CT scanning. It is valuable and promising in neck CT scan.
出处
《中国CT和MRI杂志》
2012年第3期95-98,共4页
Chinese Journal of CT and MRI
